湿陷性黄土地区新建地铁对既有结构影响研究

Research on the Influence of Newly Built Subway on Existing Structure in Collapsible Loess Area

研究目的:为研究湿陷性黄土地区隧道施工对临近既有隧道的影响,本文通过开展室内土工离心模型试验,采用控制新建盾构隧道拱顶下沉量的方法模拟隧道施工造成的地层损失量,并考虑新建隧道与既有隧道之间的间距,设置多组工况研究既有地铁隧道仰拱最大竖向位移以及围岩压力变化规律。研究结论:(1)既有隧道仰拱最大竖向位移随着地层损失率的增大及隧道净距的减小均呈线性增加规律,据此提出单线盾构穿越过程中新建隧道拱顶沉降控制标准:净距0. 5D、0. 4D、0. 3D、0. 2D工况分别为25 mm、19 mm、14. 5 mm、12. 6 mm;(2)既有隧道仰拱处比拱腰及拱顶处围岩压力减小明显,新建盾构隧道上部围岩压力有变大的趋势,新建隧道上部一定高度范围内的土层形成了拱效应;(3)研究结果与既有地铁结构仰拱实测数据进行分析对比以及优化拟合公式可为湿陷性黄土地区类似工程提供预测曲线。

Research purposes: In order to study the influence of tunnel construction on existing tunnels in collapsible loess area,the ground loss caused by tunnel construction is simulated by geotechnical centrifuge test and by controlling the vault settlement of new shield tunnel. Considering the distance between new tunnels and existing tunnels,the maximum vertical displacement of inverted arch and the variation rule of surrounding rock pressure of existing subway tunnels are studied under multiple working conditions.Research conclusions:( 1) The maximum vertical displacement of inverted arch of existing tunnels increases linearly with the increase of stratum loss rate and the decrease of net distance of tunnels. Based on this,the control criteria for vault settlement of newly built tunnels in the course of single-line shield tunneling are proposed: net distance of 0. 5 D,0. 4 D,0. 3 D and 0. 2 D is 25 mm,19 mm,14. 5 mm and 12. 6 mm,respectively.( 2) Surrounding rock pressure at inverted arch of existing tunnels decreases more obviously than that at arch waist and vault,and the pressure at the upper part of newly built shield tunnel tends to increase. Arch effect is formed in the upper part of newly built tunnel within a certain height range.( 3) The research results are analyzed and compared with the measured data of inverted arch of existing subway structure,and the optimal fitting formula can provide prediction curves for similar projects in collapsible loess area.